Impact tool torsion bar



Jan. 19, 1965 H. HoRNscHUcH 3,166,168

IMPACT TOOL. TORSION BAR Filed April l0. 1961 2 Sheets-Sheet 1 3 Hls ToRNEY Jan. 19, 1965 H. HoRNscHucH IMPACT Toor. ToRsIoN BAR 2 Sheets-Sheel'l 2 Filed April l0. 1961 FIG. 3

m ww Y mw Wm 0 m0 T H\m SY B H United States `Patent C) This invention relates to impact wrenches and particularly to such a tool having mechanism to limit the torque which it can deliver.

Tools of this general nature have been designed heretofore but an unfortunate characteristic of such tools is that they are so long that they are awkward to handle. In some designs the torque limiting mechanism is a separable piece which is apt to be still more awkward ,to handle.

It is an object of this invention to provide a compact tool cheap to manufacture and easy to adjust as to the feature of torque limitation.

Other objects and advantages of the invention will be in part obvious and in part pointed out hereinafter.

The aforesaid objects ofthe present invention, and other objects which will become apparent as the description proceeds, are achieved by providing an impact tool having a motor, a rotary hammer and a rotary anvil adapted to be struck by the hammer. There is also provided a spring means between the motor and the hammer for accumulating energy of the motor which causes the hammer to expend the accumulated energy on the anvil as an impact at a predetermined resistance to the turning of the anvil, and a torque limiting means. The torque limiting means has a ilexible member arranged to accept the turning moment ot the anvil and is fitted to receive a wrench socket, or other similar device. The torque limiting device is further provided with a means to stiften the flexible member releasably to a predetermined degree to limit the torque transmittable by the ilexible member including a rigid member for holding Van end of the iiexible member against rotation in one direction while permitting elastic rotation in the other direction, and an adjuster at the other end of the ilexible member mounted on the anvil to vary such 'stitening A preferred embodiment of the invention is described herein and shown in the accompanying drawing in which FIGURE l is a central longitudinal section through an impact tool constructed in accordance with the practice of the invention, ,Y

FIG. 2 is a perspective view of the end of thercasing with the cover removed and illustrating the manipulation of the torque limiting adjustment, Y FIG. 3 is a transverse section through FIG. l at the line 3 3 looking in the direction of the arrows, and FIG. 4 is a transverse section at the line 4 4 of FIG.

i 1 looking in the direction of the arrows.

Referring to the drawing the invention isshown as applied to an impact tool of which the impacting mechanism operates on principles very completely disclosed in United States Patent No. 2,160,150, dated May 30, 1939, granted to F. A. YIimerson et al., and being well known in the art will be described very brieily. A e

The impact tool consists of a motor ofthe pneumatic .type having a cylinder Within which is Vadaptedto revolve a rotor 12 'carrying vanes ofwhich one is lshown at i4. A housing 16 encloses the motor'and is provided with bearings 18 and 20 for rotor 12. An end 22of`rotor v12 extends beyond bearing 20 and has gear teeth 24 meshing with planet gears 26 which in turn mesh with gearrteeth on a stationary internal gear 28 having flange 30 mounted between the front and rear halves of casing 16 which are bolted together by screws-32. The planetary gears 26 Vare mounted by means of shafts 34 on .a spider 36 rotat.

ably mounted on gear 2S by means of anti-friction bearings 38. Spider 36 forms part of a hammer mechanism which includes ahammer 40 provided with jaws 42 extending longitudinally therefrom for engagement with jaws 44 of an avil member 46 rotatably mounted in housing 16 on anti-friction bearings 48.

Hammer 40 is adapted to rotate anvil 46either by continuous coupling of jaws 42 or 44 or by delivering impact therebetween when the resistance of anvil 46 to rotation exceeds some predetermined degree. The impacting in this particular instance is produced by a mechanism very completely described in the Jimerson et al. patent above mentioned in which in this instance .includes a cam Sti cut inclined or spiral on the interior surface of hammer 40 which cooperates with an oppositely inclined cam face 52 formed on the forwardly extending portion 54 of spider 36. Coil spring 56 encircling spider portion 54 is adapted to push hammer 40 in a forward direction to inter-engage jaws 42 and 44 and for this purpose spring 56 bears againstan internal shoulder S8 of hammer 40 and against a ring 6@ encircling spider portion 54 and rotatably supported without friction thereon by ball bearings 62 riding ina race 64 formed on spider 3:6.V Thus as hammer 40 is held against rotation by jaws 44, the rotation of spider 36 being continued cams hammer 4@ backwardly against the force of spring 56 due to the opposite inclinations of cam grooves 50 and 52 and the balls 62 interposed therebetween. The compression of spring 56 causes an accumulation of energy from the driving motor which increases in amount until jaws 42 are withdrawn from engagement with jaws 44.

Previous to suchdisengagement the spider 36 has continued to rotate with respect to the hammer 40 and, as the above mentioned patent describes, the energy in spring 56 becomes available to accelerate hammer 40 to catch up with spider 36 as well as to push hammer 40 forward for subsequent reenagement of jaws-42 with jaws 44. The high rotational speed imparted to hammer 40 causes a sharp blow to be struckfat jaws 44 and anvil 46. Such impact and the torquedelivered toV anvil 46 as above de scribed is adapted to be expended through a rod 64 lcoupled to anvil 46 and provided at its end with suitably squared faces 66 to receive a suitable wrench socket, screwdriver blade and the Vlike (not shown). k

Rotor 12, the hammer mechanism and anvil 46 are all hollow and in alignment and together form a central longitudinal passage68 through which rod 64 extends.Y j The coupling of rod 64 'andV lanvil 46 is accomplished by "a suitable means whereby ,oneV part may be rotated relative to the other.

Vinterior of anvil 46 meshing withV corresponding splines 72 formed on Ja .bushing memberr74 iit'ting on the endV of rod 64. In section, rod 64 is known inthe` trade as quarter-Octagon being square with the cornersV chamfered. `,Theihole in bushing 74 is llikewise quarter-Octagon Y s to receive rod 64. is ill-adapted to transfer torque from anvil46 :to its end Y66 unless or until it is wound up to aV suitable torque in amountequalling'that tobe transmitted.V When so wound up it is capable of transmitting lesser torques and up to'V that point acts as a rigid member.

A rod long and. slender bar likerod 64 When the torque to Vbe transmitted comes intermittently 'l as with the hammering mechanism .above described I meanshas to be provided to produce the eect of con- .tinued winding up of the rod 64 to the required degree.

In this instance, such meansis provided by a rigid tube l76 supported by anvil 46 and inthis instance YAformed integrally therewith and extending aboutrod 64 up to the end 66l'thereof. The end 78 of tube 76 is provided `with asquaredY aperture 80 slightly larger than rod 64 bear against the head of rod 64` which transmits the thrust also tobushing 74 through a keeper ringV S6 in rod 64 and transmit thrust onto'the head. Access to the screw 82 is provided by a recess 8S in Vhousing 16 which canbe closedfby a suitable cover 90.

Asa convenient means of turning screw 32 a'hexagonal hole is provided therein as shown at 92 which will ac, commodate an Allen-wrench 94. v 1

In order to adjust the tension `in rod Y64 it is merely necessary to hold the end 66 in avise orby a wrench and turn screw 82 the required amount. `If desired, the screw 62 may be provided with numbers as shown VVin FIG. 2 and the anvil 46 may have anindex as shown by provided .to push against hammer` and saidanvil'to cause said hammer to impact saidranvil rotatively, a torque limiting means comprising a rigid tubular member xedly attached to said anvil and Y extending through said passageway, a iiexible rod'extend- `ing the length of said impact tool supported by said Vanvil and extending through said tube to receive a wrench socket, Iscrewdriver blade and the like, and coupled to said tube adjacent such socket, and means to twist said ilexible rod at said anvil to apredeterminedrtorque value with respect to said tube. Y

2. The device asset forth in claim l in which said twisting means includes a splined coupling to vary the angular relation between said rod and said anvil and a4 screw to maintain such relation. Y

3. For an impact tool having. a motor, a rotary hammerra rotary anvil adapted torbe struck by .said ham- `mer, spring means interposed between said motor andv means` interposedbetween said motor and said hammer for accumulating energy of the motor as'vresistance toV the arrow, Suitable calibration will indicate the Vdegree ,Y

of turning.

` As has been saidrabove blows struck by the hammer `mechanism through the jaws 42 tothe jaws-44 of anvil `46 will be transmitted through rod 64 asr though' that rod -were rigid upv to the extent of the torsion initially 'Y given to that rod by turning of screw 82, That torque can be `of course applied to the workthrough the socket wrench orrother device attached to end 66. When the.

resistance Y to-tuining oit'Y the Work exceedspthat predetermined amount, rod 64 yields and there is a resultant re-Y coil of hammer Ywhich is ineffectual to produce work although it may lengthen the recoil of the hammer and possibly causaran increasedlyfpowerful blow on anvil 46. No benefit is obtained at the work siucerod 64 will yield.

Some advantage maybe taken of` the 'excessive rebound by way of mechanism to stop the operation of the Yhammer -by closing down the throttle but such'mechanism Y is not p art of this invention andis not described Yhere in detail; At 100 is indicated a trigger which may-be said hammer for accumulating energy of the motor as resistance to rotation of the anvil increases and to cause said hammer to expend such accumulated energy on said anvil as an impact at a predeterminedresistance, to turning of said anvil', a torque limitingtmeans comprising aY flexible member extending the lengthof said impact tool arranged to accept the turning moment ofv said anvil and` `iitted to receive arwrench socket, screwdriver blade', and

the like, Vand means vto stitien Vsaid member releasably to a predetermined degree to limit the torque transmittable by said member including a rigid member for holding an end of said flexible member against rotation in one direction while permitting limited rotation in the other direction, and an adjuster at the other end and mounted on said anvil to vary such stiffening.

4. For an impact tool having a motor, a rotary hammer, a rotary anvil adapted to be struck by said hammer, said motor, hammerandV anvil being in alignment and together forming a central longitudinal passage, spring rotation of the anvil increases and to cause said hammer to expend such accumulated energy on said anvil as an impactjat a predetermined resistance to turning of said anvil, a torque limiting Vmeans* comprising a flexible member disposed in said passage and extending` the length of Ysaid impact tool,- through said passage and arranged to a'cceptthe turning moment ofrsaid anvil' and tted to receive a wrench socket, screwdriver blade and the like,y andtmeans'to stien said member releasably to a predetermined degree to limit .the torque vtiansniittable by said member including a rigid member for holding an end of said iiexible member yagainst rotation in one di-` rection while permitting .limited rotation in the other direction, and an adjuster at the other end and mounted v on said anvil to vary such stiffening. I

5. For an impact tool having, a motoiya rotary" hammer, a rotary anvil adapted to be struck by said hammer,

l said motor and anvil being lin alignment and together struck by the Aend Vof hammer llt'rt'o shut down the tool in any well known manner. kThis particular torque limiting arrangement lends itself well to' such'an application sincethe recoil of hammer 4,0 at torques in rod 64 be-y low the predetermined amount have no'k particular signiicance and are relatively small, whereas upon reachg t f Ythe,predetermined torque f oijy which the .apparatus is .set

the recoil of hammer 40 becomes relatively violent. n As illustrated the housing 16` may be formedV with a suitable handle 102for manipulation Aand the throttle plunger 104 is conveniently mounted therein. v

"Thusyby the 'above construction 'are 'accomplisiied,k among others,r the objects hereinbefore referred to.

Iclaim:

l. "For an impact tool having amotor, arrotary hame-VV Vmei",l a rotary anvil, said motor, hammer and kanvil bej `ing coaxial and 'centrally apertured to `Vforni a continuons passage therethrough, means cooperative w'ithlsaid rection while permitting limited rotation in the other di,` i

t rection and anA adjuster at the other. end and mounted on4 said anvil to vary such stiiiening, a housing for saidV motor, hammer-fand anvilhavingran aperture adjacentV said'motor through which Vsaid flexible member extends..l

forming a central longitudinal passage, spring means interposed between said motor and said khammer for ac.V Y cumulating energy of the motor as Vthe resistance` tofro-j` t tation ofthe anvil increases and to cause said hammer to f expend such accumulated energy on said anvil asan. impact at a predetermined resistanceto turning ofrsaid anvil, a `torque limiting` means comprising a flexible memberY extending the length of'said impact tool ar-vv ranged to accept. the turning momentY of said` anvil and'. fitted to receive a Wrench, socket, screwdriver bladeand the like, meanstoY stiften said member Vreleasably to-a predetermined "torque to limit the torque transmittable. by said member4 including a rigid member for holding an i end of' said flexible' member againsttrotation in one di.

Y 5 6. The device as set forth in claim 4 in which said rigid member is tubular and extends longitudinally within said passage.

7. The device as set forth in claim 6 in which saidY CII housing is provided with an opening through which said exible member projects and a second opening giving access to said screw.

References Cited in the le of this patent UNTED STATES PATENTS La. Belle July 31, Peterson Oct. 22, Reynolds Feb. 11, Harrison et al. Oct. 31,

Musser Feb. 13, 

1. FOR AN IMPACT TOOL HAVING A MOTOR, A ROTARY HAMMER, A ROTARY ANVIL, SAID MOTOR, HAMMER AND ANVIL BEING COAXIAL AND CENTRALLY APERTURED TO FORM A CONTINUOUS PASSAGE THERETHROUGH, MEANS COOPERATIVE WITH SAID HAMMER AND SAID ANVIL TO CAUSE SAID HAMMER TO IMPACT SAID ANVIL ROTATIVELY, A TORQUE LIMITING MEANS COMPRISING A RIGID TUBULAR MEMBER FIXEDLY ATTACHED TO SAID ANVIL AND EXTENDING THROUGH SAID PASSAGEWAY, A FLEXIBLE ROD EXTENDING THE LENGTH OF SAID IMPACT TOOL SUPPORTED BY SAID ANVIL AND EXTENDING THROUGH SAID TUBE TO RECEIVE A WRENCH SOCKETS, SCREWDRIVER BLADE AND THE LIKE, AND COUPLED TO SAID TUBE ADJACENT SUCH SOCKET, AND MEANS TO TWIST SAID FLEXIBLE ROD AT SAID ANVIL TO A PREDETERMINED TORQUE VALUE WITH RESPECT TO SAID TUBE. 